Hydraulic system



July 28, 1959. c. V.GAGEN 2,896,589

HYDRAULICV SYSTEM Filedhuarch 5, 1958 2 Sheets-Sheet l @217 M7/MW HTTE/VEXS.

July 28 1959 c. v. GAGEN 2,896,589

HYDRAULIC`SYSTEM Filed March 5, 1958 2 Sheets-Sheet 2 INVENTOR. CHA/9L f5 C/QGEAQ United States Patent() HYDRAULIC SYSTEM Charles V. Gagen, Lafayette, Ind., assignor to Ross Gear and Tool Company, Inc., Lafayette, Ind., a corporation of Indiana Application March 5, 1958, Serial No. 719,306

Claims. (Cl. 121-465) This invention relates to hydraulic systems` such as are used, for example, in po'wer steering gears for vehicles. The invention is primarily concerned with such a system in which the control valve is biased toward its center and neutral position by a hydraulic Itorce proportional to the effort exerted by the motor of the system.

Valves for controlling systems of the type referred to are usually of one or the other of two different kinds. In the so-called open-center valve, the liquid circulates continuously, dividing in the valve to ow over two paths.

' Static pressures at points on such divided paths are transmitted respectively to opposite ends of the hydraulic motor; and, by displacing the Valve, the division of liquid between the two paths and the respective pressures therealong can be varied to cause operation of the motor. In the so-called 'closed-center type of valve, there is no flow through the valve when it is in its neutral position. Displacement of the valve from neutral position admits pressure iluid to one end of the hydraulic motor and connects the other end of the motor to exhaust.

In open-center valves, a hydraulic centering eiect biasing the valve toward its neutral position can readily be obtained in a variety of ways, using either a single reaction chamber or a pair of reaction chambers. When a single reaction chamber is used, it is usually connected to the valve-inlet, where the pressure varies in proportion to the effort exerted by the hydraulic motor. In the twochamber construction, the chambers may either be connected respectively to the two ends of the motor-cylinder with the pressures in such cylinder ends constantly acting in opposite directions on the valve or the two chambers can both be connected to the valve-inlet and the valve so constructed that the pressure in one chamber is ineffective to oppose the Valve-centering pressure in the other chamber.

Such flexibility in the design of hydraulic centering mechanism is not possible in closed-center valves, where the pressure at the valve-inlet is usually at a maximum when the valve is in its neutral position. Prior hydraulically centered valves of the closed-center type have there- [fore customarily embodied two reaction chambers connected respectively to the opposite ends of the motorcylinder, so that the hydraulic valve-centering effort would be proportional to the differences in the respective pressures at the opposite ends of the motor cylinder.

It is the principal object of this invention to provide a simple construction whereby a valve of the closed center type can be hydraulically urged toward its neutral position by the use of a single reaction chamber.

In carrying out my invention in its preferred form I use a sliding spool-type valve which, in its neutral position, cuts off all communication between the source of pressure uid and the motor, but which can be displaced in either direction from such neutral position to connect one end of the motor-cylinder to the pressure-source and the other end of the motor cylinder to exhaust. The passages through which the valve ports are connected with the opposite ends of the motor cylinder are arranged to ICC communicate in common with a reaction chamber under the fcontrol of a shuttle-type valve which is responsive to pressure dilerences between the two ends of the motor cylinder to connect the reaction chamber to the highpressure end of the motor cylinder and interrupt communication between the reaction chamber and the low-pressure end of the motor cylinder. Through such a shuttle valve the hydraulic pressure in the reaction chamber will always be substantially equal to the pressure in the highpressure end of the motor cylinder and hence proportional to the effort exerted by the motor. Mechanism of any convenient type provided in the reaction chamber functions to cause the hydraulic pressure therein to urge the valve toward its neutral position.

In the accompanying drawing, which illustrates a preferred embodiment of the invention:

Fig. 1 is an end elevation of the body of a spool-type valve mechanism;

Fig. 2 is a side elevation of the valve mechanism;

Fig. 3 is a transverse section on the broken line 3 3 of Fig. 2;

Fig. 4 is a transverse section on the line 4-4 of Fig. 2;

Fig. 5 is an axial section on the line 5-5 of Fig. l;

Fig, 6 is a fragmental axial section on the line 6 6 of Fig. l; and

Fig. 7 is a diagrammatic view illustrating the entire hydraulic system and the manner in `which my valve is embodied in it.

The valve shown in the dra'wing comprises a body 10 having a longitudinally extending bore 11 which slidably receives a spool valve 12. The valve 12 is rigid with a stem 13 projecting from one end of the bore through a cover 14.

Interiorly, the valve-body 10 is provided with three annular, axially spaced grooves including an intermediate groove 16 and two end grooves 17 and 18. The valve body 12 is provided with two annular grooves 20 and 21 dening an intermediate land 22 and two end lands 23 and 24. In the neutral position of the valve the intermediate land 22, which is wider than the groove 16, is coplanar with such groove and therefore closes it, while the end land 23 closes the groove 17 and the end land 24 closes the groove 18.

Displaced from the bore 11, the valve-body 10` is provided with a transverse inlet passage Z6 and a transverse exhaust passage 27, both adapted at their outer ends for connection respectively to fluid supply and fluid return conduits. The exhaust passage 27 is located substantially in the plane of the groove 17, communicates therewith, and extends beyond to join a passage 28 communicating 1n turn 'with the end groove 18. The inlet passage 26 is located substantially in the plane of the groove 16 and communicates therewith, but does not continue on through the valve body to join the passage 28.

Extending longitudinally of the vave `'body parallel to Ithe valve 'bore 11 and, as shown, opening into the end face 30 of the valve body, are a pair of passages 31 and 32. The passage 31 opens at its inner end into the bore 11 between the grooves 16 and 18 to communicate with the -groove 21 of the valve spool. The passage 32, at its inner end, opens into the bore 11 between the grooves 16 and 17 to communicate with the valvegroove 20.

In Fig. 7, I have illustrated the valve as so far described embodied in a simple hydraulic system including a motor having a cylinder 35 and piston 36. In such arrangement, the passage 32 in the valve body 10 is connected through passage or conduit 32 to the left-hand end of the cylinder 35 while the passage 31 is connected through passage or conduit 31 to the right-hand end of such cylinder. The inlet passage 26 is connected :through a conduit 37 with the outlet of a pump 38, while the 3 inlet of such pump is connected through a conduit 39 with the outlet passage 27 of the valve-body. The two conduits 37 and 39 are interconnected through a by-pass conduit ifi including a pressure-regulating valve 4l.

When the valve i2 is in its neutral position, its intermediate landl occludes the groove I6 which is connected to the outlet of the pump 38, with the result that liquid discharged from the pump is compelled to circulate through conduit 40 and pressure-regulating valve 41, the setting of which determines the pressure maintained in `the conduit 37 and valve-inlet passage 26. If the valve l2 is displaced from -neutral position toward the right, the -groove 20 interconnects the passages 26 and 32, while the groove 2l interconnects the passages 3l and 28-27. Liquid discharged fromV the pump therefore flows -by way of conduit 37, valve passages Z6 and 32, and conduit 32 to displace thel piston 36 to the right forcing liquid from the right-hand end of the cylinder 35 through conduit 31', passages 3l, 28, and 27, and conduit 39 to the inlet of the pump. In similar fashion, displacement of the valve to the left of its neutral position connects ythe passage 26 with the passage 31 and the passage 32 with the passage 27', whereupon liquid will flow to the right-hand end of the cylinder 35 to move the piston 36 to the left, and liquid from the left-hand end of the cylinder will be returned through conduit 32', passages 32 and Z7, and conduit 39 to the pump.

As previously indicated, it is the purpose of my invention to associate with the valve mechanism which will operate to urge the valve toward neutral position when it has Ibeen displaced in either direction therefrom, and to so urge the valve with a force dependent upon the effort exerted yby the motor 35-36. To that end, I provide the valve-body .l with an annular reaction chamber 45, and I provide means whereby such reaction chamber will be connected to that one of the passages 3i and 32 'in which the higher hydraulic pressure exists. As shown, the valve-body i@ is provided with a passage 46 (Fig. 4) which extends transversely between the passages 31 and 32 tangentially of the chamber 45. Within the passage 46 and rbetween the passages 31 and 32 I dispose a sleeve 47 having a central chamber 48 communicating through a port 49 with `the reaction chamber 45. Extending axially of the sleeve from the chamber 48 are aligned passages 5f) and 51 connecting the chamber 49 with the passages 31 and 32, respectively. The passages 50 and 5I are of smaller diameter than the chamber iti and the openings through which they communicate with such chamber form valve seats for a valve 53, shown as a metal ball, Such ball is freely movable axially of the sleeve 47 between the two valve seats.

When the valve i2. is moved from neutral position to effect operation of the motor 35-36, the pressure in one of the passages 3i and 32 will become higher than that in 'the other, and such excess pressure will result in displacing the -valve 53 into engagement with that valve seat through which the chamber i8 communicates with the passage (3f or 32) of lower pressure, leaving free communication between the other passage and the chamber 4S. As the chamber 48 is in free communication through port a9 with the reaction chamber 45, the pressure in the chamber 45 will always correspond with the higher of the two pressures respectively existing in the passages 3l and 32.

The arrangement shown for utilizing pressure in the chamber 45 to urge the valve l2 toward neutral position comprises inner and outer annular spring abutments 55 and 56. The inner abutment 55 is adapted to seat against outwardly presented shoulders which are provided on the valve 1.2. and body ifi and which are coplanar with each other when the valve is in neutral position. The outer abutment, which has sealing engagement with the wall of the chamber i and with the valve l2, is adapted to seat against inwardly presented shoulders on the valve 12 and body, such inwardly presented shoulders also being coplanar with each other when the valve is in neutral position. A compression spring 57 acts between the abutments 55 and 56 to urge them away from each other.

As will be obvious, any displacement of the valve 12 in either direction from neutral position will both compress the spring 57 and reduce the effective volume of the chamber 45. Accordingly the displaced valve will be urged to return to neutral position both by the spring and `by hydraulic pressure in the chamber. I rely on the spring merely to provide a minimum valve-centering effort effective even if no, or little, pressure exists in the chamber 45. When the motor 35--36 is operating against substantial load the pressure in the high-pressure end of cylinder 45 is applied to t-he chamber 45, and, as above set forth, 'will create a `valve-centering effort proportional to the load. The absolute value of the hydraulic centering force for any given pressure in .the chamber 45 will depend upon the respective diameters of the bore 11 and chamber 45, as the hydraulic pressure in the chamber is effective over an annu-lar area whose inner diameter is that of the valve bore and whose outer diameter -is that of the chamber.

I claim as my invention:

l. In a hydraulic system including a source of liquid under pressure, a motor havin-g a cylinder and a piston reciprocable therein, a valve, first and second passages connecting said valve to opposite ends of said cylinder, a supply passage connecting said source to said valve, said valve including a body and a reciprocable element movable in opposite directions from a neutral position in said body to direct liquid from the supply passage alternatively into said first and second passages, said valve element when in neutral position preventing liquid flow from said supply passages, hydraulic means including a pressure chamber for urging said valve element toward neutral position when displaced therefrom, and an auxiliary valve means operable in response to differences of pressure in said first and second passages for connecting said chamber to the passage in which the higher pressure exists.

2. In a hydraulic system including a source of liquid under pressure, a motor having a cylinder and a piston reciprocable therein, a valve, first and second passages connecting said valve to opposite ends of said cylinder, a supply passage connecting said source to said valve, said valve including a body and a reciprocable element movable in opposite directions from a neutral position in said body to direct liquid from the supply passage alternatively into said first and second passages, said valve element when in neutral position preventing liquid flow from said supply passages7 Lhydraulic means including a pressure chamber for urging said valve element toward neutral position when displaced therefrom, a cross passage interconnecting said first and second passages, a pair of spaced valve seats in said cross passage, and a valve member freely movable between said valve seats under the influence of pressure differences in said first and second passages, said chamber communicating with a point in said cross passage between said valve seats.

3. A valve for controlling a reversible hydraulic motor, comprising a body having a bore and an inlet port communicating with said bore, said bore having first and second passages adapted for connection to the motor, a reciprocable valving element in said bore movable from a neutral position in opposite directions to connect said inlet port alternatively to said passages, said body having a chamber, means responsive to hydraulic pressure in said chamber for urging said valving element toward its neutral position when displaced therefrom, and auxiliary valve means within said body responsive to differences of pressure in said first and second passages for connecting said chamber to the passage in which the higher pressure exists.

4. A valve for controlling a reversible hydraulic motor, comprising a body having a bore and an inlet port communicating With said bore, said bore having first and second passages adapted for connection to the motor, a reciprocab'le valving element in said bore movable from a neutral position in opposite directions to connect said inlet port alternatively to said passages, said body having a chamber, means responsive to hydraulic pressure in said chamber for urging said valving element toward its neutral position when displaced therefrom, said body also having a cross passage interconnecting said rst and second passages, alpair of spaced valve seats in said cross passage, and a valve member freely movable between said valve seats under the influence of pressure differences in said first and second passages, said charnber communicating with a point in said cross passage between said valve seats.

5. A valve as set forth in claim 4 further characterized in that said valving element is longitudinally reciprocable in said bore, said chamber being :located adjacent one end of said bore, said rst and second passages extending from said bore substantially parallel to the axis thereof and past said chamber, said cross passage being substantially coplanar with said first and second passages and disposed generally tangentially of said chamber.

References Cited in the le of this patent UNITED STATES PATENTS 2,345,531 De Ganahl Mar. 28, 1944 2,380,705 Proctor July 31, 1945 2,393,585 Boynton et al. Jan. 29, 1946 2,757,748 MacDut Aug. 7, 1956 

